The present invention relates to gravity filters, and particularly to gravity filters using multiple underdrain blocks to define laterals. More particularly, the present invention relates to gravity filters having multiple underdrain block laterals that employ a backwash cycle for cleaning.
Gravity filters, used to filter water or other influents, commonly use underdrain blocks to support a filter media, and provide convenient flow paths into and out of the filter media. The underdrain blocks are arranged in rows commonly called laterals. The laterals are arranged side-by-side to cover the bottom of the filter. Water enters the gravity filter, flows through the filter media and into the underdrain block laterals. The filtered water, or filtrate, flows along the underdrain laterals to an outlet. To facilitate removal of the filtrate, gravity filters commonly employ a flume disposed perpendicular to and beneath the underdrain laterals. An opening in each underdrain lateral connects the lateral to the flume, which carries the filtrate out of the filter.
Periodically, gravity filters require a backwash cycle to clean the filter media and improve the filter effectiveness. During a backwash cycle, a backwash liquid, commonly water, flows into the individual laterals and into the filter media. The fluid passes through the laterals and the filter media in substantially the opposite direction as the influent flow. The backwash liquid removes contaminates and other debris that clogs the filter media.
To improve the effectiveness of the backwash cycles, it is common to introduce a gas, typically air, with the backwash liquid flow. Air and water are used in conjunction or individually to perform the periodic backwash cycles.
Introducing air into the underdrain laterals currently requires the use of a separate air supply header within the flume with risers or drop tubes feeding the individual underdrain laterals. The air supply header, risers, and drop tubes disrupt flow within the flume and filter by taking up flow space. Therefore, it is desirable to provide an apparatus that allows for the introduction of both liquid and gas for backwashing of the filter media without requiring an additional, separate header or complicated wall penetrations.
Thus, according to the present invention, a filter provides a cuboidal block including an outer wall defining an inner chamber and a block exterior. A typical cuboidal block is defined by the extrusion of a square or rectangular cross section along an axis. The filter also includes a conduit having a conduit wall, a first conduit end, a second conduit end, and an inner flow path providing fluid communication between the first and second conduit ends. The conduit wall includes an orifice therethrough. The conduit is coupled to the block such that the first conduit end is in fluid communication with the inner chamber of the block and the second conduit end and the orifice are in fluid communication with the block exterior.
The invention further provides a method of backwashing a filter. The filter includes a cuboidal block having an inner chamber and a block exterior. The conduit also includes a first end in fluid communication with the inner chamber of the block and a second end in fluid communication with the first end. The wall of the conduit has an orifice therethrough, the orifice and second end disposed in the block exterior. The method comprises disposing the second end of the conduit in a reservoir. The method further includes providing a backwash liquid to the reservoir and providing a backwash gas to the reservoir. The air and gas supply is pressurized such that the liquid supply enters the second end of the conduit and the gas selectively enters the conduit through the orifice. The liquid and gas pass through the conduit and into the block.
In preferred embodiments, the blocks interconnect to define laterals. A filter having a base supports the laterals in a side-by-side relationship with the laterals substantially covering the base. A flume formed in the base of the filter extends beneath each lateral. The conduit, which is preferably a round pipe, extends into the flume such that one end of the conduit and the conduit orifices are disposed within the flume.
Additional features and advantages will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.